1. Field of Art
The disclosure generally relates to video compression, more particularly, to improvements in video coding efficiency using internal bit depth extension and reference frame compression.
2. Description of the Related Art
Recent video compression development indicates increasing bit depth during encoding process improves video coding efficiency. According to existing video coding experimental results (e.g., TOSHIBA's adaptive scaling scheme), by using 12 bits of internal bit depth for an 8-bit video input, over 10% of bitrate saving for some 720p (“p” stands for “progressive”) and 1080p video sequences can be achieved compared to compression without increasing bit depth. The most coding gain comes from improvements in inter-frame prediction using an internal bit depth increase (IBDI) scheme.
IBDI technique refers to increasing the bit depth of pixels of a video sequence at the input to an encoder and adjusting the bit depth at the output of a decoder. IBDI can be used to improve standard elements of a block-based video codec (e.g., H.264 video coding) including arithmetic precision of prediction, transform and loop filter.
It is known that pixel bit depth has a direct impact on memory access bandwidth and capacity of the reference frame buffers used during the video encoding and decoding processes. One approach is to efficiently compress the IBDI reference frames so that the adverse impact on memory access and capacity of the frame buffers is minimized while maintaining most of the coding gain. Such an approach is referred to as reference frame compression (RFC). The existing IBDI codec faces a major challenge to balance the coding gain from bit depth increase against the adverse impact on implementation complexity. The challenges faced by the existing IBDI codec call for a system and method for improved adaptive bit depth scaling and efficient IBDI reference frame compression.